1. Field of the Invention
The present invention relates generally to belt drives and more specifically to a tensioning device that can quickly and easily tension a belt or endless drive element used to transmit power between a vehicle and its driven attachment.
2. Description of the Related Art
Vehicles such as lawn and garden tractors are commonly used in combination with implements such as rotary mowers. These implements are frequently powered by an endless drive element such as a belt. The belts are entrained about a pair of pulleys, one pulley being coupled with a shaft either driven by or powered by the engine crankshaft and the other pulley being coupled with a shaft on the implement. To maintain tension on the belt and ensure transmission of power between the shafts and their pulleys, one shaft is movable relative to the other and a tensioning device is used to urge them apart.
Changes in the tension of belts are commonly required when an implement is installed, removed, the belts are replaced or they stretch due to wear. Since the implements are often adapted to be adjusted vertically and/or laterally with respect to the vehicle, the relative positions of the two shafts and their pulleys will change, also requiring occasional adjustments to the belt tension.
One common method of tensioning such belts utilizes a driven pulley swingably mounted on a shaft carried by the implement with a biasing mechanism for urging the shaft and its pulley away from the driving shaft. The driving shaft is typically mounted for rotation in bearings with both shafts being mounted in a cantilevered arrangement to allow them to carry a pulley at their outer end portion. Since these biasing mechanisms serve to urge the shaft and its driven pulley away from the driving shaft and its pulley to increase the belt tension, the resulting forces transferred to the end portions of the two shafts by the belt tension serve to urge the ends of the shafts toward one another with bending forces being encountered at the end portions of the shafts. These bending forces vary as the implement is adjusted relative to the vehicle.
The bending forces not only accelerate wear between the shafts and their respective bearing supports, but can also cause complete bearing failures. Since the crankshaft often serves as the driving shaft, the bearings which support it inside the engine can fail, resulting in substantial repair expense.
For these reasons, it would be desirable to provide a tensioning mechanism that will reduce or minimize the bending forces transferred to the two shafts as the belt is tensioned, and also provide a relatively constant tensioning force as the position of the implement is vertically and/or laterally adjusted relative to the vehicle.
Towards these ends, there is provided a tensioning device usable with generally parallel and spaced apart first and second shaft members, wherein one member is movable relative to the other and each supports a pulley carried on a cantilevered end portion. It is effective to urge the shaft members apart and provide tension to an endless belt element entrained about the pulleys.
The tensioning device extends between and engages each shaft member so that the forces urging the shaft members apart are applied directly to the shaft members to minimize the bending forces imposed upon their cantilevered end portions.
It maintains engagement with the shaft members as the implement is adjusted vertically and/or laterally relative to the vehicle so that forces exerted on the members remains relatively constant.
Provision is made for adjusting the degree of force exerted on the shaft members by the tensioning device to accommodate belt wear, the amount of belt drive force required for transmitting power under different conditions and compensate for adjustment of the implement.
A quick-release capability is included to allow the device to be rapidly and easily installed, secured in place and/or removed. The device is simple, has few parts and can be utilized with a variety of drive and driven shaft member configurations, irrespective of whether they are oriented vertically, horizontally or otherwise.
The tensioning device of the preferred embodiment includes first and second slideable members coupled together and extending between first and second shaft members having respective pulleys with a belt entrained thereabout. One of the shaft members is movable relative to the other to permit adjustment of the distance between the shaft members and tensioning of the endless drive member. An end portion of each slideable member is removably engaged with a seat provided on each shaft member that facilitates quick and easy coupling with and/or removal from the shaft members and also allow vertical and lateral adjustment of one shaft member relative to the other.
The slideable members are provided with a compression spring that urges them and their engaged shaft members apart with adjustment capability being provided to change the level of force exerted by the device. An overcenter locking mechanism is provided to allows the tensioning device to be quickly and easily installed or removed. A latching structure serves to releasably secure the overcenter locking mechanism and tensioning device in its operative configuration.